If you had your own private Mijin chain you could have all the mosaics you could want for your game (and other games too and it would be fine). You would be able to service millions of accounts with millions of transactions per days and fees to set mosaics and tx fees would be 0 out of pocket expenses. Transactions would also clear with blocks that were exactly 15 seconds apart. What would cost you is the monthly Mijin server fees to run your own private ledger.
The good thing about a Mijin ledger though is that any of your apps could connect to it and the users would all have control over their own tokens. It would also scale extremely well and all for 1 set monthly cost. (I’m not sure what that is right now, but I was aware that Mijin was for a time offering 6 months of free service for a while).